The present application claims priority to Japanese Application No. P11-009892 filed Jan. 18, 1999, which application is incorporated herein by reference to the extent permitted by law.
The present invention relates to a magnetic resistance element using a magnetic tunneling effect and also to a novel magnetic device using the magnetic resistance element.
There has been a report of a magnetic tunneling effect in which the conductance of a tunnel current flowing through a thin insulating layer depends on a relative angle of magnetization of both magnetic layers in a three-layer structure consisting of magnetic metal, an insulating layer, and magnetic metal.
In this phenomenon, the magnetic resistance ratio can be logically calculated by polarizabilities of both magnetic layers. For example, in case of using Fe for both magnetic layers, an MR ratio of about 40% can be expected.
Further, in recent years, there have successively been reports teaching that a large MR ratio is realized at a room temperature, which have attracted a great attention as a new device.
Meanwhile, a change of resistance is achieved by making two magnetic layers parallel with other or anti-parallel with each other in a magnetic tunneling element which had appeared before. Mainly used as methods for realizing this are a method of making a difference in coercive force between two magnetic layers and a method of approximating an anti-ferromagnetic layer to a magnetic layer thereby to pin motion of magnetization.
However, in these methods, the resistance transits between a case of high resistance in a state in which directions of magnetization are aligned in parallel with each other and a case of low resistance in a state in which the directions are aligned in anti-parallel with each other, so that no stable state exists halfway. Therefore, these methods are disadvantageous when multivaluing the memory.
The present invention has been proposed in consideration of the conventional situation as described above and has an object of providing a magnetic resistance element capable of realizing a more excellent magnetization array condition than a conventional element, and further an object of providing a magnetic device using the same.
To achieve the above object, in a magnetic resistance element according to the present invention, a first magnetic layer, which is formed in contact with an anti-ferromagnetic layer, and at least two magnetic layers are layered such that tunnel barrier wall layers are respectively inserted between the first magnetic layer and the at least two magnetic layers.
For example, if the at least two magnetic layers are formed of second and third magnetic layers, four kinds of magnetization array states exist.
The magnetic resistance element described above is applicable to various magnetic devices such as a magnetic memory, a magnetic head, and the like.
As is apparent from the above explanation, according to the present invention, it is possible to realize a magnetic resistance element having four or more kinds of magnetization array states in case where no external magnetic field exists.
In this magnetic resistance element, the magnetization array states are controlled by an external magnetic field and each state can be selected freely. Further, by applying a sense magnetic field of a specific pattern, it is possible to detect which magnetization array state is selected.
Accordingly, multivalued recording can be achieved by utilizing the magnetic resistance element for a magnetic memory and a magnetic head, the recordable information amount can be remarkably increased.